In the Victorian era, people made their cores look tight by wearing corsets, which doubled as bulletproof vests during pistol duels. Strengthen your core until it's naturally impervious to bullets instead with today's Groupon: for $30, get four semiprivate Pilates or gravity strength classes from Gravity Central Fitness in Newington (a $100 value).

Gravity Central Fitness uses its special gravity training system to create efficient, powerful workouts. Similar in appearance to a jungle gym slide hooked to a pulley system by a local kid genius, the GTS unit engages multiple muscle groups via an adjustable incline and biomechanically sound exercises. Classes are limited to five people, giving every fitness fan an experience that combines the individualized attention of a certified trainer with the motivating hive mind of a group class. Sample-happy fitness fans can mix and match classes between gravity Pilates and strength training. Pilates focuses on spinal alignment, strength, flexibility, neuromuscular control, and telepathy, while gravity strength training bulks up all the major muscle groups and is an especially good fit for those who usually focus on cardio. Wide expanses of window and exposed brick cause the gymnasium to give off a hip, industrial aroma. Contact Gravity Central Fitness to find out about available class times.